Such transport belts are known for the conveyance of articles in a multiplicity of areas. Depending on the nature of the articles to be transported, for example luggage in airports, groceries at supermarket checkouts, bulk materials in mining, etc., these conveyor belts must meet different requirements. What is required in the longitudinal direction is, on account of the generally fairly long conveying distances, a minimum of extensibility combined with a degree of flexibility to allow guidance along a drive and deflecting drum In the transverse direction, flat-running conveyor belts should be very stiff The properties of the transport belt in respect of tensile strength, extensibility and transverse stiffness are essentially determined by the textile layers which act as load-bearing and strength components The incorporation of a plurality of layers of flat fabrics is an attempt to achieve the desired strength together with a long life However, as the number of fabric layers increases, the thickness of the transport belt also increases, which has an adverse effect on the drive system. The various fabric layers tend to slip relative to one another, as a result of which a stretching of the material is unavoidable Similarly, the embedding of the fabric layers presents problems in respect of the necessary attachment by impregnation with a plastic or rubber. EP-A-0,280,118 therefore proposes using, for the weaving of the textile fabric, threads which are already covered as a whole or in part by a layer of rubber or a rubberlike material, to improve the attachment of the cover layers to the embedded layer. If pretreated threads are used, the manufacture of such transport belts is costly. In addition, only the attachment of the load-bearing and strength component is changed and not its property profile for the transport belt. It is still necessary to incorporate a plurality of textile layers.
To obtain the desired overall strength, flat-running conveyor belts are also manufactured using high-tenacity yarns for the textile layers. They confer on the fabric low extensibility and high breaking strength in the longitudinal and transverse directions, but require the use of expensive yarns. However, the transverse stiffness of these conveyor belts, if flat fabrics are incorporated in one or two layers, is still insufficient, so that heavier articles cause the conveyor belt to trough in the middle. This is a disadvantage, for example in respect of processing and packaging stations arranged along the transport path. In addition, the unquiet running and the associated noise does not meet the requirements of an environment-friendly conveyance of articles.
EP-A-0,051,750, finally, discloses a conveyor belt which contains as the only strength component spaced-apart steel wires which extend in the longitudinal direction in a parallel arrangement. In addition, the upper and/or lower cover layer contain an air-filled hollow body as a cushioning layer in order that the impact energy of piece goods may be absorbed. The cushioning layer is formed by a double cloth composed of two parallel lengths of fabric which are kept spaced apart by pile threads distributed over the entire area and which are sealed off to the outside along the side edges over the entire length of the belt. It is true that such a cushioning layer in the form of a compound fabric makes it possible to enclose a volume of air, but it cannot absorb any tensile forces. On the contrary, owing to the flexibility of the spaced-apart double cloth, it is necessary to incorporate a separate strong reinforcing layer. In particular, the transverse stiffness remains inadequate, despite the reinforcing layer, which is a disadvantage for flat-running transport belts.